A pollution index is currently featuring four Indian cities in the 25 most polluted places in the world
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/lucknow-most-polluted-city-world-three-other-indian-cities-feature-25-most-polluted-cities
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/daily-news-analysis-mumbai
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/lucknow-d
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/kolkata
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/meerut-d
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/mumbai
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/maharashtra
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/uttar-pradesh
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/water-pollution
[11] http://admin.indiaenvironmentportal.org.in/category/thesaurus/china
[12] http://admin.indiaenvironmentportal.org.in/category/thesaurus/spm
[13] http://admin.indiaenvironmentportal.org.in/category/thesaurus/health-effects
[14] http://admin.indiaenvironmentportal.org.in/category/thesaurus/respiratory-diseases
[15] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment